Metal powder, method of producing additively-manufactured article, and additively-manufactured article

ABSTRACT

A metal powder contains not less than 0.10 mass % and not more than 1.00 mass % of at least one of chromium and silicon, and a balance of copper. The total content of the chromium and the silicon is not more than 1.00 mass %. In accordance with an additive manufacturing method for this metal powder, an additively-manufactured article made from a copper alloy is provided. The additively-manufactured article has both an adequate mechanical strength and an adequate electrical conductivity.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a metal powder, a method of producingan additively-manufactured article, and an additively-manufacturedarticle.

Description of the Background Art

Japanese Patent Laying-Open No. 2011-21218 discloses a laseradditive-manufacturing apparatus (so-called “3D printer”) for metalpowder.

SUMMARY OF THE INVENTION

The additive manufacturing method for metal powder is of interest as aprocessing technology for metal products. An advantage of this method isthat complicated shapes which have been impossible by cutting work canbe produced. Examples of additively-manufactured articles produced fromiron-based alloy powder, aluminum alloy powder, titanium alloy powder,and the like have heretofore been reported. Currently, however, thekinds of metals available for additive manufacturing are limited, andthere is a certain restriction on metal products to which additivemanufacturing is applicable.

An object of the present invention is to provide a metal powder of acopper alloy for additive manufacturing, a method of producing anadditively-manufactured article, and an additively-manufactured article,exhibiting both an adequate mechanical strength and an adequateelectrical conductivity.

[1] The metal powder is a metal powder for additive manufacturing. Themetal powder contains: not less than 0.10 mass % and not more than 1.00mass % of at least one of chromium and silicon, a total content of thechromium and the silicon being not more than 1.00 mass %; and a balanceof copper.

[2] The metal powder of the above [1] may contain: not less than 0.10mass % and not more than 0.60 mass % of the chromium; and a balance ofthe copper.

[3] The metal powder of the above [1] may contain: not less than 0.10mass % and not more than 0.60 mass % of the silicon; and a balance ofthe copper.

[4] The method of producing an additively-manufactured article includes:a first step of forming a powder layer including a metal powder of anyof the above [1] to [3]; and a second step of forming a shaped layer bysolidifying the metal powder at a predetermined position in the powderlayer. The first step and the second step of this production method aresuccessively repeated to stack the shaped layers and produce anadditively-manufactured article.

[5] The method of producing an additively-manufactured article of theabove [4] may further include a heat treatment step of heat-treating theadditively-manufactured article.

[6] The additively-manufactured article is an additively-manufacturedarticle produced from a metal powder of any of the above [1] to [3]. Theadditively-manufactured article is preferably heat-treated after beingadditively manufactured.

[7] The additively-manufactured article is an additively-manufacturedarticle made from a copper alloy. The copper alloy contains: not lessthan 0.10 mass % and not more than 1.00 mass % of at least one ofchromium and silicon, a total content of the chromium and the siliconbeing not more than 1.00 mass %; and a balance of copper. Theadditively-manufactured article has a relative density of not less than96% and not more than 100% with respect to a theoretical density of thecopper alloy, and has an electrical conductivity of not less than 26%IACS.

[8] As to the above [7], the copper alloy may be a chromium-containingcopper alloy containing: not less than 0.10 mass % and not more than0.60 mass % of the chromium; and a balance of the copper. In this case,the additively-manufactured article has a relative density of not lessthan 96% and not more than 100% with respect to a theoretical density ofthe chromium-containing copper alloy, and has an electrical conductivityof not less than 30% IACS.

[9] As to the above [7], the copper alloy may be a silicon-containingcopper alloy containing: not less than 0.10 mass % and not more than0.60 mass % of the silicon; and a balance of the copper. In this case,the additively-manufactured article has a relative density of not lessthan 96% and not more than 100% with respect to a theoretical density ofthe silicon-containing copper alloy, and an electrical conductivity ofnot less than 26% IACS.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart generally showing a method of producing anadditively-manufactured article according to an embodiment of thepresent invention.

FIG. 2 is a schematic diagram showing an example of STL data.

FIG. 3 is a schematic diagram showing an example of slice data.

FIG. 4 is a first schematic diagram illustrating a process of producingan additively-manufactured article.

FIG. 5 is a second schematic diagram illustrating the process ofproducing an additively-manufactured article.

FIG. 6 is a third schematic diagram illustrating the process ofproducing an additively-manufactured article.

FIG. 7 is a fourth schematic diagram illustrating the process ofproducing an additively-manufactured article.

FIG. 8 is a plan view showing a test specimen used for a tensile test.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, an embodiment of the present invention (hereinafterreferred to as “the present embodiment”) will be described. The presentinvention, however, is not limited thereto.

Initially, how the inventors of the present invention attained thepresent embodiment will be described.

For mechanical parts required to have an adequate mechanical strengthand an adequate electrical conductivity, mostly copper is used. Examplesof such mechanical parts may for example be parts of welding torch,electric power distribution facility, and the like. The inventorsatomized an ingot of pure copper to thereby obtain a copper powder, andtried to produce an additively-manufactured article from this copperpowder. A desired additively-manufactured article, however, could not beobtained by this method. Specifically, the produced article had manyvoids and the density of the article was significantly decreasedrelative to that of the original ingot. Further, the electricalconductivity of the article was also significantly decreased relative tothat of the original ingot. The decrease of the density is considered asinevitably resulting in decrease of the mechanical strength. Theinventors tried to improve physical properties by changing variousconditions. As long as the pure copper was used, however, the finalphysical properties were not stable even under the same conditions, andit was impossible to obtain both an adequate mechanical strength and anadequate electrical conductivity.

The inventors then studied copper alloys. As a result, the inventorsfound that a copper alloy powder having a specific alloy compositioncould be used to produce an additively-manufactured article having bothan adequate mechanical strength and an adequate electrical conductivity.

“Having both an adequate mechanical strength and an adequate electricalconductivity” herein means that an additively-manufactured articlesatisfies all of the following conditions (a) to (c).

(1) The tensile strength is approximately equal to or more than 195 MPa.Namely, the tensile strength is approximately equivalent to or more thanthat of an ingot of oxygen-free copper (UNS No.: C10200). The tensilestrength is measured through the following procedure. For measurement ofthe tensile strength, a tension testing machine of Grade one or moreunder “JIS B 7721: Tension/compression testing machines—verification andcalibration of the force-measuring system” is used. A dumbbell-shapedtest specimen 20 shown in FIG. 8 is manufactured. Dumbbell-shaped testspecimen 20 is tensioned at a rate of 2 mm/min by using the tensiontesting machine until the test specimen is broken. At this time, as agripping tool or jig, any tool appropriate for the shape ofdumbbell-shaped test specimen 20 is used. Adjustments are further madeso that a force is applied in the axial direction of dumbbell-shapedtest specimen 20. The maximum tensile stress detected before the testspecimen is broken is measured. The maximum tensile stress is divided bythe cross-sectional area of a parallel portion 21 to thereby calculatethe tensile stress. The cross-sectional area of parallel portion 21 is9.616 m² (=π×3.5 mm×3.5 mm/4). The dimensions of respective parts ofdumbbell-shaped test specimen 20 are as follows.

total length L0 of dumbbell-shaped test specimen 20: 36 mm

length L1 of parallel portion 21: 18±0.5 mm

diameter D1 of parallel portion 21: 3.5±0.05 mm

radius R of shoulder portion 23: 10 mm

length L2 of grip portion 22: 4.0 mm

diameter D2 of grip portion 22: 6.0 mm

(b) The relative density with respect to the theoretical density is 96%or more. The theoretical density of an alloy herein refers to thedensity of a cast material and having the same composition as the alloy.The relative density with respect to the theoretical density is a valuein percentage determined by dividing the actually measured density ofthe additively-manufactured article by the theoretical density of thealloy.

(c) The electrical conductivity is 26% IACS or more, with respect to theelectrical conductivity 100% IACS (International Annealed CopperStandard) of an annealed copper standard. Namely, the electricalconductivity is approximately equivalent to or more than that of aningot of brass (UNS No: C26000).

[Metal Powder]

The metal powder of the present embodiment is a metal powder foradditive manufacturing. The metal powder corresponds to toner/ink for acommon two-dimensional printer. The metal powder contains: not less than0.10 mass % and not more than 1.00 mass % of at least one of chromium(Cr) and silicon (Si), a total content of Cr and Si being not more than1.00 mass %; and a balance of copper (Cu). The Cu content in the metalpowder may for example be not less than 98 mass %, not less than 98.5mass %, or not less than 99.0 mass %.

The Cu content in the metal powder can be measured by a method complyingwith “JIS H 1051: Copper and copper alloys—Determination of coppercontent.” The Cr content can be measured by an ICP emission spectrometrycomplying with “JIS H 1071: Methods for determination of chromium incopper and copper alloys.” The Si content can be measured by an ICPemission spectrometry complying with “JIS H 1061: Methods fordetermination of silicon in copper and copper alloys.” The upper limitof at least one of Cr and Si in the metal powder may be 0.90 mass %,0.80 mass %, 0.70 mass %, or 0.60 mass %. The lower limit of at leastone of Cr and Si may be 0.15 mass %, or 0.20 mass %.

The metal powder may contain an impurity element besides Cu Cr, and Si.The impurity element may be an element (additive element) intentionallyadded during production. Namely, in the metal powder of the presentembodiment, the balance may be Cu and an additive element. The impurityelement may also be an element (incidental impurity) incidentally mixedduring production. Namely, in the metal powder of the presentembodiment, the balance may be Cu and an incidental impurity.Alternatively, the balance may be Cu, an additive element, and anincidental impurity. Examples of the impurity element may be oxygen (O),phosphorus (P), and the like. The content of the impurity element mayfor example be less than 0.10 mass %, or less than 0.05 mass %.

The metal powder of the present embodiment includes for example achromium-containing copper alloy powder and a silicon-containing copperalloy powder as detailed below.

Chromium-Containing Copper Alloy Powder

The chromium-containing copper alloy powder contains not less than 0.10mass % and not more than 0.60 mass % of Cr, and a balance of Cu. Asdescribed above, the balance may further include an additive elementand/or an incidental impurity. An additively-manufactured articleproduced from this copper alloy powder having such a chemicalcomposition can be expected to be improved particularly in electricalconductivity. In the chromium-containing copper alloy powder, the lowerlimit of the Cr content may for example be 0.15 mass %, 0.20 mass %, or0.25 mass %. The upper limit of the Cr content may for example be 0.55mass %, or 0.50 mass %. The Cr content may for example be not less than0.22 mass % and not more than 0.51 mass %. In the case where the Crcontent falls in these ranges, the additively-manufactured article mayhave well-balanced mechanical strength and electrical conductivity.

Silicon-Containing Copper Alloy Powder

The silicon-containing copper alloy powder contains not less than 0.10mass % and not more than 0.60 mass % of Si, and a balance of Cu. Asdescribed above, the balance may include an additive element and/or anincidental impurity. An additively-manufactured article produced fromthis copper alloy powder having such a chemical composition can beexpected to be improved particularly in mechanical strength. In thesilicon-containing copper alloy powder, the lower limit of the Sicontent may for example be 0.15 mass %, 0.20 mass %, or 0.25 mass %. Theupper limit of the Si content may for example be 0.55 mass %, or 0.50mass %. The Si content may for example be not less than 0.21 mass % andnot more than 0.55 mass %. In the case where the Si content falls inthese ranges, the additively-manufactured article may have well-balancedmechanical strength and electrical conductivity.

Particle-Size Distribution

The particle-size distribution of the metal powder is appropriatelyadjusted based on conditions for producing the powder, sizing, sieving,or the like. The average particle size of the metal powder may beadjusted in accordance with the pitch at which layers are stacked toproduce an additively-manufactured article. The average particle size ofthe metal powder may for example be approximately 100 to 200 μm,approximately 50 to 100 μm, or approximately 5 to 50 μm. The averageparticle size herein refers to a particle size at a cumulative value of50% (so-called “d50”) in a particle-size distribution measured by thelaser diffraction/scattering method. The particle shape of the metalpowder is not particularly limited. The particle shape may be asubstantially spherical shape or an irregular shape.

Method of Producing Metal Powder

The metal powder of the present embodiment is produced for example by agas atomization method or a water atomization method. Namely, whilealloy components in the molten state are dropped from the bottom of atundish, the alloy components are allowed to contact high-pressure gasor high-pressure water, and the alloy components are rapidly cooled tobe solidified. In this way, the alloy components are formed intoparticles. Alternatively, plasma atomization method, centrifugalatomization method, or the like may for example be used to produce themetal powder. The metal powder obtained through these production methodstends to enable a dense additively-manufactured article to be obtained.

[Method of Producing Additively-Manufactured Article]

In the following, a method of producing an additively-manufacturedarticle from the above-described metal powder will be described. Here, adescription will be given of a powder bed fusion method using a laser asmeans for solidifying the metal powder. This means, however, is notlimited to the laser as long as the means can solidify the metal powder.The means may for example be electron beam, plasma, or the like. In thepresent embodiment, an additive manufacturing (AM) method other than thepowder bed fusion method may be used. For example, in the presentembodiment, the directed energy deposition method may also be used.Further, in the present embodiment, cutting may be performed duringadditive manufacturing.

FIG. 1 is a flowchart generally showing a method of producing anadditively-manufactured article of the present embodiment. Thisproduction method includes a data processing step (S10) and an additivemanufacturing step (S20). The production method may also include a heattreatment step (S30) after the additive manufacturing step (S20). Theadditive manufacturing step (S20) includes a first step (S21) and asecond step (S22). According to this production method, the first step(S21) and the second step (S22) are successively repeated to therebyproduce an additively-manufactured article. The method will be describedhereinafter with reference to FIGS. 1 to 7.

1. Data Processing Step (S10)

First, three-dimensional shape data is produced by 3D-CAD or the like.The three-dimensional shape data is converted to STL data. FIG. 2 is aschematic diagram showing an example of STL data. In STL data 10 d,division into elements (meshing) is done by the finite-element method,for example.

From the STL data, slice data is produced. FIG. 3 is a schematic diagramshowing an example of slice data. The STL data is divided into n layers,namely a first shaped layer p1 to an n-th shaped layer pn. The slicethickness d is approximately 10 to 150 μm for example.

2. Additive Manufacturing Step (S20)

Subsequently, based on the slice data, an additively-manufacturedarticle is produced. FIG. 4 is a first schematic diagram illustrating aprocess of producing an additively-manufactured article. A laseradditive-manufacturing apparatus 100 shown in FIG. 4 includes a piston101, a table 102 supported on piston 101, and a laser emission unit 103.This step and subsequent steps are carried out in an inert gasatmosphere for example for suppressing oxidation of theadditively-manufactured article. The inert gas may for example be argon(Ar), nitrogen (N₂), helium (He), or the like. Instead of the inert gas,a reducing gas such as hydrogen (H₂) for example may be used. Moreover,a vacuum pump or the like may be used to produce a reduced-pressureatmosphere.

Piston 101 is configured to be capable of lifting and lowering table102. On table 102, the additively-manufactured article is produced.

2-1. First Step (S21)

In the first step (S21), a powder layer including the metal powder isformed. Based on the slice data, piston 101 lowers table 102 by adistance corresponding to one layer. On table 102, the metal powdercorresponding to one layer is spread. In this way, a first powder layer1 including the metal powder is formed. The surface of first powderlayer 1 is smoothed by means of a squeezing blade or the like (notshown). The powder layer may include multiple kinds of metal powders.For example, the powder layer may include both the chromium-containingcopper alloy powder and the silicon-containing copper alloy powder asdescribed above. The powder layer may also include a laser absorber(resin powder for example) or the like, in addition to the metal powder.The powder layer may be substantially made up of only the metal powder.

2-2. Second Step (S22)

FIG. 5 is a second schematic diagram illustrating the process ofproducing an additively-manufactured article. In the second step (S22),a shaped layer which is to form a part of the additively-manufacturedarticle is formed.

Laser emission unit 103 applies a laser beam to a predetermined positionin first powder layer 1, based on the slice data. Before the laser beamis applied, the powder layer may be heated in advance. The metal powderirradiated with the laser beam is melted and sintered and accordinglysolidified. In this way, the metal powder at a predetermined position infirst powder layer 1 is solidified to thereby form first shaped layerp1.

As the laser emission unit of the present embodiment, a general-purposelaser device may be used. As a laser beam source, a fiber laser, a YAGlaser, a CO₂ laser, a semiconductor laser, or the like is used. Thelaser beam output power may for example be approximately 100 to 1000 W,or approximately 200 to 500 W. The laser beam scanning velocity may beadjusted within a range for example of 100 to 1000 mm/s. The laser beamenergy density may be adjusted within a range for example of 100 to 1000J/mm³.

The laser beam energy density herein refers to a value calculated inaccordance with the following expression (I):E=P/(v×s×d)  (I).In expression (I), E represents laser beam energy density [unit: J/mm³],P represents laser output power [unit: W], v represents scanningvelocity [unit: mm/s], s represents scanning width [unit: mm], and drepresents slice thickness [unit: mm].

FIG. 6 is a third schematic diagram illustrating the process ofproducing an additively-manufactured article. As shown in FIG. 6, afterfirst shaped layer p1 is formed, piston 101 further lowers table 102 bya distance corresponding to one layer. After this, a second powder layer2 is formed in a similar manner to the above-described one, and a secondshaped layer p2 is formed based on the slice data. After this, the firststep (S21) and the second step (S22) are repeated. FIG. 7 is a fourthschematic diagram illustrating the process of producing anadditively-manufactured article. As shown in FIG. 7, finally the n-thshaped layer pn is formed and thus an additively-manufactured article 10is thus completed.

3. Third Step (S30)

Preferably, the additively-manufactured article is thereafterheat-treated. Namely, it is preferable for the additively-manufacturedarticle to be heat-treated after additively manufactured. The heattreatment can be expected to improve the mechanical properties and theelectrical conductivity of the additively-manufactured article. Theatmosphere during the heat treatment may for example be an atmosphere ofnitrogen, air, argon, hydrogen, vacuum, or the like. The heat treatmenttemperature may for example be not less than 300° C. and not more than400° C. The time for heat treatment may for example be not less than twohours and not more than four hours.

[Additively-Manufactured Article]

In the following, a description will be given of anadditively-manufactured article obtained in accordance with theabove-described production method. The additively-manufactured articlemay have a shape which cannot be obtained by cutting. Moreover, theadditively-manufactured article of the present embodiment has both anadequate mechanical strength and an adequate electrical conductivity.The additively-manufactured article of the present embodiment isapplicable to a plasma torch by way of example.

In the case where the metal powder of the present embodiment is used asa raw material, the additively-manufactured article may have thefollowing composition.

Namely, the additively-manufactured article of the present embodiment isan additively-manufactured article made from a specific copper alloy.The copper alloy contains: not less than 0.10 mass % and not more than1.00 mass % of at least one of chromium and silicon, a total content ofthe chromium and the silicon being not more than 1.00 mass %; and abalance of copper. Like the metal powder, the balance of the copperalloy may include an additive element and/or an incidental impurity. Theadditively-manufactured article has a relative density of not less than96% and not more than 100% with respect to the theoretical density ofthe copper alloy, and has an electrical conductivity of not less than26% IACS.

In the copper alloy, the upper limit of the content of at least one ofCr and Si may be 0.90 mass %, 0.80 mass %, 0.70 mass %, or 0.60 mass %.The lower limit of the content of at least one of Cr and Si may be 0.15mass % or 0.20 mass %.

The density of the additively-manufactured article can for example bemeasured in accordance with the Archimedes method. The densitymeasurement in accordance with the Archimedes method may be done tocomply with “JIS Z 2501: Sintered metal materials—Determination ofdensity, oil content and open porosity.” Water may be used as theliquid.

In the case where the relative density with respect to the theoreticaldensity is not less than 96%, a mechanical density adequate forpractical use can be expected. A higher relative density is desired. Therelative density of the additively-manufactured article may be not lessthan 96.5%, not less than 97.0%, not less than 97.5%, not less than98.0%, not less than 98.5%, or not less than 99.0%.

The electrical conductivity can be measured by means of acommercially-available eddy-current conductivity meter. A higherelectrical conductivity is also desired. The electrical conductivity ofthe additively-manufactured article may be not less than 30% IACS, notless than 40% IACS, not less than 50% IACS, or not less than 60% IACS.The upper limit of the electrical conductivity may for example be 100%IACS.

Additively-Manufactured Article Made from Chromium-Containing CopperAlloy

In the case where the chromium-containing copper alloy powder of thepresent embodiment is used as a raw material, theadditively-manufactured article may have the following composition.

Namely, the additively-manufactured article is anadditively-manufactured article made from a specific chromium-containingcopper alloy. The chromium-containing copper alloy contains not lessthan 0.10 mass % and not more than 0.60 mass % of Cr and a balance ofCu. Like the metal powder, the balance of the chromium-containing copperalloy may include an additive element and/or an incidental impurity. Theadditively-manufactured article has a relative density of not less than96% and not more than 100% with respect to the theoretical density ofthe chromium-containing copper alloy, and has an electrical conductivityof not less than 30% IACS. In the case where the Cr content of theadditively-manufactured article is not less than 0.10 mass % and notmore than 0.30 mass %, the additively-manufactured article can beexpected to have both a relative density of not less than 98% and anelectrical conductivity of not less than 60% IACS.

Additively-Manufactured Article Made from Silicon-Containing CopperAlloy

In the case where the silicon-containing copper alloy powder of thepresent embodiment is used as a raw material, theadditively-manufactured article may have the following composition.

Namely, the additively-manufactured article is anadditively-manufactured article made from a specific silicon-containingcopper alloy. The silicon-containing copper alloy contains not less than0.10 mass % and not more than 0.60 mass % of Si and a balance of Cu.Like the metal powder, the balance of the silicon-containing copperalloy may include an additive element and/or an incidental impurity. Theadditively-manufactured article has a relative density of not less than96% and not more than 100% with respect to the theoretical density ofthe silicon-containing copper alloy, and has an electrical conductivityof not less than 26% IACS. In the case where the Si content of theadditively-manufactured article is not less than 0.10 mass % and notmore than 0.30 mass %, the additively-manufactured article can beexpected to have both a relative density of not less than 98.5% and anelectrical conductivity of not less than 45% IACS.

EXAMPLES

In the following, the present embodiment will be described withExamples. The present embodiment, however, is not limited to them.

1. Preparation of Metal Powder

Metal powders A1, A2, A3, B1, B2, X, and Y each containing the chemicalcomponents shown in Table 1 were prepared.

TABLE 1 List of Metal Powders d50 chemical components (μm) A1 Cr (0.22mass %); O (0.09 mass %); Cu (balance) 25.0 A2 Cr (0.51 mass %); O (0.04mass %); Cu (balance) 25.0 A3 Cr (0.94 mass %); O (0.05 mass %); Cu(balance) 20.7 B1 Si (0.21 mass %); O (0.01 mass %); P (0.01 mass %);26.0 Cu (balance) B2 Si (0.55 mass %); O (0.03 mass %); P (less than0.01 27.7 mass %); Cu (balance) X Cu (99.99 mass % or more) 21.3 Y Ni(2.52 mass %); Si (0.71 mass %); Cr (0.31 mass %); 20.0 Cu (balance)

These metal powders were produced in accordance with a predeterminedatomization method. Metal powders A1, A2, A3, B1, and B2 correspond toexamples of the present invention.

Metal powder X was produced from an ingot of a commercially-availablepure-copper. Metal powder Y was produced from an ingot of acommercially-available copper alloy (product name “AMPCO940”). Metalpowder X and metal powder Y correspond to comparative examples.

2. Laser Additive-Manufacturing Apparatus.

A laser additive-manufacturing apparatus with the followingspecifications was prepared.

Laser: fiber laser, maximum output power 400 W

Spot diameter: 0.05 to 0.20 mm

Scanning velocity: not more than 7000 mm/s

Layer stack pitch: 0.02 to 0.08 mm

Maximum build size: 250 mm×250 mm×280 mm

3. Production of Additively-Manufactured Article

The above-described apparatus was used to produce anadditively-manufactured article having a columnar shape (diameter 14mm×height 15 mm).

3-1. Commercially-Available Pure Copper Powder

Following the flow shown in FIG. 1, the first step (S21) of forming apowder layer including the metal powder, and the second step (S22) offorming a shaped layer by applying a laser beam at a predeterminedposition in the powder layer to thereby solidify the metal powder weresuccessively repeated to produce the additively-manufactured articles ofNo. X-1 to No. X-40. Conditions for producing eachadditively-manufactured article are shown in Table 2 and Table 3.

In accordance with the above-described methods, the relative density andthe electrical conductivity of each additively-manufactured article weremeasured. The results are shown in Table 2 and Table 3.

TABLE 2 Commercially-Available Pure Copper production method 1st 2ndstep additively-manufactured article step laser irradiation after heatpowder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS X-1X 200 587.3 unmeasurable — 49.58 — X-2 X 200 587.3 unmeasurable — 64.72— X-3 X 200 587.3 unmeasurable — 50.44 — X-4 X 200 587.3 unmeasurable —65.85 — X-5 X 200 587.3 96.723 — 85.24 — X-6 X 200 587.3 92.260 — 67.21— X-7 X 200 587.3 unmeasurable — 48.89 — X-8 X 200 587.3 unmeasurable —64.95 — X-9 X 300 391.5 unmeasurable — 63.13 — X-10 X 300 391.5unmeasurable — 63.59 — X-11 X 300 391.5 unmeasurable — 67.89 — X-12 X300 391.5 unmeasurable — 65.63 — X-13 X 300 391.5 unmeasurable — 58.15 —X-14 X 300 391.5 unmeasurable — 68.12 — X-15 X 300 391.5 unmeasurable —64.04 — X-16 X 300 391.5 unmeasurable — 61.32 — X-17 X 400 293.7unmeasurable — 70.51 — X-18 X 400 293.7 unmeasurable — 63.13 — X-19 X400 293.7 unmeasurable — 75.21 — X-20 X 400 293.7 unmeasurable — 66.15 —X-21 X 400 293.7 unmeasurable — 62.68 — X-22 X 400 293.7 92.215 — 67.67— X-23 X 400 293.7 unmeasurable — 71.14 — X-24 X 400 293.7 unmeasurable— 63.13 —

TABLE 3 Commercially-Available Pure Copper production method 2nd stepadditively-manufactured article 1st step laser irradiation after heatpowder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS X-25X 500 234.9 unmeasurable — 73.64 — X-26 X 500 234.9 unmeasurable — 62.00— X-27 X 500 234.9 93.054 — 82.10 — X-28 X 500 234.9 unmeasurable —64.27 — X-29 X 500 234.9 unmeasurable — 64.04 — X-30 X 500 234.9unmeasurable — 65.40 — X-31 X 500 234.9 unmeasurable — 75.21 — X-32 X500 234.9 unmeasurable — 62.23 — X-33 X 600 195.8 unmeasurable — 89.46 —X-34 X 600 195.8 unmeasurable — 73.96 — X-35 X 600 195.8 98.311 — 92.58— X-36 X 600 195.8 unmeasurable — 75.21 — X-37 X 600 195.8 unmeasurable— 61.77 — X-38 X 600 195.8 unmeasurable — 75.21 — X-39 X 600 195.898.311 — 90.24 — X-40 X 600 195.8 unmeasurable — 73.33 —

As seen from Table 2 and Table 3, additively-manufactured articlesproduced from pure-copper powder (metal powder X) significantly varyfrom one another in final physical properties even under the sameconditions. “Unmeasurable” in Table 2 means that a highly reliabledensity could not be measured by the Archimedes method due to anexcessively large number of voids. The electrical conductivity of apure-copper ingot may be considered as approximately 100% IACS. Theadditively-manufactured articles produced from the pure copper aresignificantly lower in electrical conductivity than the ingot of thepure copper. Based on these results, it is considered difficult toproduce a practically applicable mechanical part from the pure copperpowder.

3-2. Commercially-Available Copper Alloy Powder

Under the conditions shown in Table 4, additively-manufactured articlesof No. Y-1 to No. Y-7 were produced in a similar manner to theabove-described one. Conditions for producing eachadditively-manufactured article are shown in Table 4.

In accordance with the above-described methods, the relative density andthe electrical conductivity of each additively-manufactured article weremeasured. The results are shown in Table 4.

TABLE 4 Commercially-Available Copper Alloy production method 2nd stepadditively-manufactured article 1st step laser irradiation after heatpowder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS Y-1Y 400 156.3 99.03% — — — Y-2 Y 400 156.3 98.98% — 15.97 18.23 Y-3 Y 400156.3 99.07% — 15.97 18.23 Y-4 Y 400 156.3 99.30% — — — Y-5 Y 800 192.799.23% — 15.93 18.37 Y-6 Y 800 192.7 99.49% — 15.97 18.50 Y-7 Y 800192.7 99.33% — — —

The additively-manufactured articles produced from thecommercially-available copper alloy powder (metal powder Y) had a higherdensity than that of the pure copper. The additively-manufacturedarticles, however, had an electrical conductivity significantly lowerthan that of the original material (approximately 45.5% IACS).

3-3. Chromium-Containing Copper Alloy Powder

3-3-1. Cr=0.22 Mass %

Under the conditions shown in Table 5, additively-manufactured articlesof No. A1-1 to No. A1-11 were produced in a similar manner to theabove-described one. Further, after the additively-manufactured articlewas produced, the article was heat-treated (S30). Conditions for theheat treatment included a nitrogen atmosphere and 300° C.×3 hours (thesame conditions are applied to the following heat treatment). Thephysical properties of each additively-manufactured article wereevaluated. The results of evaluation are shown in Table 5. The tensilestrength was measured by means of a test specimen, namely adumbbell-shaped test specimen 20 shown in Table 8 which was producedseparately, under the conditions shown for No. A1-12 to No. A1-14 (thesame is applied as well to the following tensile strength).

TABLE 5 Cr-Containing Cu alloy (Cr = 0.22 mass %) production method 1st2nd step additively-manufactured article step laser irradiation afterheat powder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS A1-1A1 200 587.3 96.395 — 55.88 62.57 A1-2 A1 300 391.5 97.167 — 57.62 63.93A1-3 A1 400 293.7 97.173 — 56.63 62.68 A1-4 A1 500 234.9 97.352 — 56.3162.00 A1-5 A1 600 195.8 97.967 — 56.42 62.00 A1-6 A1 700 167.8 97.027 —56.31 61.78 A1-7 A1 600 274.1 98.241 — 59.40 63.47 A1-8 A1 600 228.498.353 215.02 60.42 64.27 A1-9 A1 600 195.8 97.967 — 56.42 62.00 A1-10A1 600 171.3 96.457 — 55.13 59.34 A1-11 A1 600 152.3 96.708 — 56.9561.09 A1-12 A1 500 234.9 — 198.56 — — A1-13 A1 600 195.8 — 219.78 — —A1-14 A1 700 167.8 — 186.74 — —

As seen from Table 5, variation of the final physical properties amongthe additively-manufactured articles produced from the copper alloypowder containing 0.22 mass % of chromium (metal powder A1) could besuppressed, as compared with the additively-manufactured articlesproduced from the pure copper as described above. Theseadditively-manufactured articles produced from the copper alloy powder(metal powder A1) had both a practically adequate mechanical strengthand a practically adequate electrical conductivity. With thiscomposition, a high electrical conductivity of 60% IACS or more could beobtained after heat treatment.

3-3-2. Cr=0.51 Mass %

Under the conditions shown in Table 6, additively-manufactured articlesof No. A2-1 to No. A2-12 were produced. The physical properties of eachadditively-manufactured article were evaluated. The results ofevaluation are shown in Table 6.

TABLE 6 Cr-Containing Cu alloy (Cr = 0.51 mass %) production method 1st2nd step additively-manufactured article step laser irradiation afterheat powder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS A2-1A2 200 587.3 98.952 — 33.26 36.86 A2-2 A2 300 391.5 99.243 — 32.95 36.99A2-3 A2 400 293.7 99.199 — 33.01 37.17 A2-4 A2 500 234.9 99.484 — 33.3837.41 A2-5 A2 600 195.8 99.484 — 33.75 37.66 A2-6 A2 500 274.1 99.361 —33.28 37.50 A2-7 A2 600 228.4 99.596 — 33.01 37.56 A2-8 A2 500 234.999.277 — 33.44 37.99 A2-9 A2 600 195.8 99.255 — 33.10 38.12 A2-10 A2 500234.9 — 250.7 — — A2-11 A2 600 195.8 — 250.2 — — A2-12 A2 600 195.8 —243.8 — —

As seen from Table 6, variation of the final physical properties amongthe additively-manufactured articles produced from the copper alloypowder containing 0.51 mass % of chromium (metal powder A2) could besuppressed, as compared with the additively-manufactured articlesproduced from the pure copper as described above. Theseadditively-manufactured articles produced from the copper alloy powder(metal powder A2) had both the denseness given by a relativeconductivity of more than 99% and an electrical conductivity of morethan 35% IACS. The additively-manufactured articles also had an adequatetensile strength.

3-3-3. Cr=0.94 Mass %

Under the conditions shown in Table 7, additively-manufactured articlesof No. A3-1 to No. A3-7 were produced. The physical properties of eachadditively-manufactured article were evaluated. The results ofevaluation are shown in Table 7.

TABLE 7 Cr-Containing Cu Alloy (Cr = 0.94 mass %) production method 1st2nd step additively-manufactured article step laser irradiation afterheat powder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS A3-1A3 200 587.3 99.250 — 23.92 26.35 A3-2 A3 300 391.5 99.064 — 23.64 26.25A3-3 A3 400 293.7 99.176 — 23.64 26.41 A3-4 A3 500 234.9 99.101 — 23.5926.44 A3-5 A3 600 195.8 99.228 — 23.92 26.63 A3-6 A3 200 587.3 — 281.41— — A3-7 A3 600 195.8 — 266.60 — —

As seen from Table 7, variation of the final physical properties amongthe additively-manufactured articles produced from the copper alloypowder containing 0.94 mass % of chromium (metal powder A3) could besuppressed, as compared with the additively-manufactured articlesproduced from the pure copper as described above. Theseadditively-manufactured articles produced from the copper alloy powder(metal powder A3) had both a practically adequate mechanical strengthand a practically adequate electrical conductivity. With thiscomposition, denseness given by a relative density of more than 99%could be obtained. The additively-manufactured articles also had anadequate tensile strength.

3-4. Silicon-Containing Copper Alloy Powder

3-4-1. Si=0.21 Mass %

Under the conditions shown in Table 8, additively-manufactured articlesof No. B1-1 to No. B1-11 were produced. The physical properties of eachadditively-manufactured article were evaluated. The results ofevaluation are shown in Table 8.

TABLE 8 Si-Containing Cu Alloy (Si = 0.21 mass %) production method 1st2nd step additively-manufactured article step laser irradiation afterheat powder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS B1-1B1 200 587.3 97.484 — 46.92 47.00 B1-2 B1 300 391.5 98.587 — 47.40 47.32B1-3 B1 400 293.7 97.523 — 47.08 47.08 B1-4 B1 500 234.9 97.484 — 47.0846.60 B1-5 B1 600 195.8 97.019 — 46.81 46.52 B1-6 B1 700 167.8 96.789 —46.36 45.81 B1-7 B1 200 685.2 98.694 — 48.37 48.30 B1-8 B1 300 548.198.750 — 47.89 48.55 B1-9 B1 300 391.5 98.587 — 47.40 47.32 B1-10 B1 300391.5 — 218.35 — — B1-11 B1 400 293.7 — 228.27 — —

As seen from Table 8, variation of the final physical properties amongthe additively-manufactured articles produced from the copper alloypowder containing 0.21 mass % of silicon (metal powder B1) could besuppressed, as compared with the additively-manufactured articlesproduced from the pure copper as described above. Theseadditively-manufactured articles produced from the copper alloy powder(metal powder B1) had both a practically adequate mechanical strengthand a practically adequate electrical conductivity. With thiscomposition, a high electrical conductivity of 45% IACS or more could beobtained.

3-4-2. Si=0.55 Mass %

Under the conditions shown in Table 9, additively-manufactured articlesof No. B2-1 to No. B2-8 were produced. The physical properties of eachadditively-manufactured article were evaluated. The results ofevaluation are shown in Table 9.

TABLE 9 Si-Containing Cu Alloy (Si = 0.55 mass %) production method 1st2nd step additively-manufactured article step laser irradiation afterheat powder conditions treatment layer scanning energy relative tensileelectrical electrical metal velocity density density strengthconductivity conductivity No. powder mm/s J/mm³ % MPa % IACS % IACS B2-1B2 100 1174.6 97.020 — 25.65 — B2-2 B2 200 587.3 97.660 — 27.32 — B2-3B2 300 391.5 97.735 — 27.23 26.91 B2-4 B2 400 293.7 97.773 — 27.92 27.61B2-5 B2 400 293.7 99.144 236.98 28.56 27.91 B2-6 B2 500 234.9 99.098235.03 28.62 28.01 B2-7 B2 600 195.8 99.158 — 28.52 27.82 B2-8 B2 700167.8 98.717 — 28.15 27.70

As seen from Table 9, variation of the final physical properties amongthe additively-manufactured articles produced from the copper alloypowder containing 0.55 mass % of silicon (metal powder B2) could besuppressed, as compared with the additively-manufactured articlesproduced from the pure copper as described above. Theseadditively-manufactured articles produced from the copper alloy powder(metal powder B2) had both a practically adequate mechanical strengthand a practically adequate electrical conductivity. With thiscomposition, denseness given by a relative density of more than 99%could be obtained.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the scopeof the present invention being interpreted by the terms of the appendedclaims.

What is claimed is:
 1. A method of producing an additively-manufacturedarticle, the method comprising: a first step of forming a powder layerconsisting of a copper alloy powder, the copper alloy powder consistingof not less than 0.10 mass % and not more than 1.00 mass % of at leastone of chromium and silicon, a total content of the chromium and thesilicon being not more than 1.00 mass %, and a balance of copper, anelement besides the copper, the chromium, and the silicon being lessthan 0.10 mass %; and a second step of forming a shaped layer by meltingand/or sintering the copper alloy powder so that metal particlesincluded in the copper alloy powder fuse directly to each other at apredetermined position in the powder layer, the first step and thesecond step being successively repeated to stack the shaped layers andproduce an additively-manufactured article.
 2. The method of producingan additively-manufactured article according to claim 1, furthercomprising a heat treatment step of heat-treating theadditively-manufactured article.
 3. The method of producing anadditively-manufactured article according to claim 1, wherein the copperalloy powder comprises more than 0.51 mass % and not more than 0.94 mass% of chromium; and a balance of copper.
 4. The method of producing anadditively-manufactured article according to claim 1, wherein in thesecond step, the copper alloy powder is melted and/or sintered byirradiating the copper alloy powder with at least one selected from thegroup consisting of a laser, an electron beam and plasma.
 5. A method ofproducing an additively-manufactured article, the method comprising: afirst step of forming a powder layer consisting of a copper alloypowder, the copper alloy powder consisting of not less than 0.22 mass %and not more than 0.94 mass % of chromium, not less than 98.0 mass % ofcopper, and an impurity element, the impurity element being an elementbesides the copper and the chromium, the impurity element being lessthan 0.10 mass %, and a second step of forming a shaped layer by meltingand/or sintering the copper alloy powder so that metal particlesincluded in the copper alloy powder fuse directly to each other at apredetermined position in the powder layer, the first step and thesecond step being successively repeated to stack the shaped layers andproduce an additively-manufactured article.
 6. The method of producingan additively-manufactured article according to claim 5, wherein thecopper alloy powder comprises not less than 98.5 mass % of copper. 7.The method of producing an additively-manufactured article according toclaim 5, wherein the copper alloy powder comprises not less than 99.0mass % of copper.
 8. The method of producing an additively-manufacturedarticle according to claim 5, wherein the copper alloy powder comprisesmore than 0.51 mass % and not more than 0.94 mass % of chromium.
 9. Themethod of producing an additively-manufactured article according toclaim 5, wherein in the second step, the copper alloy powder is meltedand/or sintered by irradiating the copper alloy powder with at least oneselected from the group consisting of a laser, an electron beam andplasma.